Energy and Metabolism Chapter 8

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Energy and MetabolismChapter 8
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Energy

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Energy
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Energy
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Metabolism

• All the chemical reactions carried out by the cell

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Metabolism

• Catabolic reactions
• Break down large molecules into smaller
  substances
• Exergonic
• Releases energy

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Metabolism

• Anabolic reactions
• Synthesis of large molecules from smaller
  substances
• Endergonic
• Requires energy

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Metabolism

• Biochemical pathways
• Reactions in a cell
• Occur in sequence
• Product of one reaction
• Becomes substrate in the next
• Pathways are highly regulated and coordinated
• Feedback inhibition
• End product of a reaction blocks the pathway from
  producing more.

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Energy
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Energy

• Bioenergetics
• Analysis of how energy powers activities of
  living systems
• Growth, order, reproduction, responsiveness
  regulation

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Energy

• Energy
• The capacity to do work
• Kinetic energy
• Energy of motion
• Potential energy
• Energy of position or stored energy

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Energy

• Kinetic energy
• Potential energy

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Energy

• Thermodynamics 
• Study of energy heat changes
• Most work done by living organisms
• Transformation of PE to KE

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Energy

• Sun main source of energy
• Energy from sun
• Combine smaller molecules to make larger
  molecules
• Energy is stored in the chemical bond

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Energy

• Redox(oxidation-reduction) reactions
• Transfer of an electron or electrons
• Play a key role in the flow of energy in
  biological systems
• An electron is passed from one atom to another
  energy is passed

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Law of thermodynamics

• Laws of thermodynamics govern all energy changes
  in the universe.
•  First law of thermodynamics
• Energy cannot be created or destroyed
• Change from one form to another. (potential to
  kinetic)
• Total amount of energy stays the same

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First law

• In living organisms
• Eating transfers energy from the bonds in food to
  organism
• PE is transferred to KE

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First Law

• Heat
• Random motion of molecules
• Heat can be lost in the system during conversions
• Sun replaces energy lost as heat

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Second law

• Second law of thermodynamics
• Transformation of PE to heat (random motion of
  molecules).
• Entropy (disorder) in the universe is increasing

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Second law

• Energy transformations tend to proceed
  spontaneously
• Convert matter from a more ordered state to a
  less ordered or more stable state.

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Second law

• Entropy(s)
• Disorder in a system
• Enthalpy (H)
• Heat content
• Free energy(G)
• Amount of energy available to do work in any
  system.
• Amount of energy available to break and then make
  other chemical bonds

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Second law

• GGibbs free energy
• ?G ??H - T?S (TKelvin temp)
• ?G is positive
• Products have more energy than reactants
• Due to more energy in the bonds or less
  randomness
• Endergonic reaction

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Endergonic reaction
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Second law

• ?G is negative
• Products have less energy than reactants
• H is lower (bond energy) or
• S is greater- more randomness
• Exergonic
• Reaction that releases energy

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Exergonic reaction
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Exergonic reactions
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Activation Energy

• Energy needed to initiate a reaction
• All reactions require activation energy.
• Reactions with higher AE tend to move forward
  more slowly

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Enzymes

• Catalyst in living organisms
• Large three-dimensional globular protein
• Ribozymes
• RNA catalysts are specific speed up reactions

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Enzymes

• Substrate
• Molecule that is going to undergo the reaction
• Active sites
• Specific spots on the enzyme that substrates
  binds
• Enzyme-substrate complex
• Enzymes are bound to substrates with a precise
  fit.
• Induced fit
• When the substrate causes the enzyme to adjust to
  make a better fit
• ES ES E P

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Fig. 8-17
Substrates enter active site enzyme
changes shape such that its active site enfolds
the substrates (induced fit).
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Substrates held in active site by
weak interactions, such as hydrogen bonds
and ionic bonds.
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Substrates
Enzyme-substrate complex
Active site can lower EA and speed up a
reaction.
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Active site is available for two
new substrate molecules.
Enzyme
Products are released.
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4
Substrates are converted to products.
Products
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Enzymes

• Only small amounts are necessary
• Can be recycled
• Specific
• Speeds up the reactions
• Different types of cells have different enzymes
• Determine the course of chemical reactions in the
  cell

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Enzyme examples

• Lipase, protease
• Carbonic anhydrase
• CO2 H2O H2CO3
• Lactate dehydrogenase
• Lactate to pyruvate
• Pyruvate dehydrogenase
• Enzyme that starts the Kreb cycle

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Enzymes

• Factors that affect the rate of enzyme
• 1. Concentration of enzyme substrate
• 2. Factors that affect 3-D shape of the enzyme
• Temperature, pH, salt concentration and
  regulatory molecules

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Enzymes

• Inhibitor
• Binds the enzyme
• Prevents it from working
• Occurs at the end of a pathway to stop the
  reactions
• Two types of inhibitors
• Competitive
• Noncompetitive

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Fig. 8-19
Substrate
Active site
Competitive inhibitor
Enzyme
Noncompetitive inhibitor
(a) Normal binding
(c) Noncompetitive inhibition
(b) Competitive inhibition
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Enzymes

• Allosteric site
• On/off switch for the enzyme
• Usually at different location than the active
  site
• Allosteric inhibitor
• Binds at the allosteric site
• Stops the enzyme activity
• Activators
• Binds increases the activity

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Enzymes

• Cofactor
• Assists enzyme function such as Zn, Mg, Cu
• Coenzymes
• Cofactors that are not proteins but are organic
  molecules
• Help transfer electrons energy associated with
  the electrons
• Vitamins are coenzymes
• NAD important coenzyme

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Energy
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ATP

• ATP powers the energy requiring processes in the
  cell
• 1. Chemical work (making polymers)
• 2. Transporting substances
• 3. Mechanical work
• Muscle movement, cilia

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ATP

• Structure of ATP
• Ribose sugar
• Adenine
• 3 phosphate attached in a row

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ATP
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ATP

• ATP
• ADP
• Losses a inorganic phosphate
• Hydrolysis
• 7.3kcal/mole of energy is released.